Knowledge of viscosity of liquid metals and alloys is valuable pratically and theoretically, and accuratedata should be particularly important on the consideration of the structure of liquid metals andalloys. An accurate measurement of viscosity, however, especially on high temperature such as on liquidiron is quite difficult and most of the data having been obtained may be dcubtful in their reliability.For the purpose of carrying out precise measurement of viscosity of liquid metals and alloys at hightemperature an improved apparatus for viscosity measurement by oscillating crucible method wasmade, and through the experiments using this apparatus some fundamental problems on the viscositymeasurement were analytically examined and discussed.The main results obtained are summarized as follows:
(1) From an analysis of the oscillation modes on distilled water, n-heptane and liquid mercury, itwas concluded that oscillation periods shorter than about 4 seconds should not be employed for themeasurement because of the occurrence of the irregular flow in liquid. The most reliable result wasobtained at the periods of about 7 seconds on present apparatus.
(2) The atmosphere used in the viscosity measurement is very important factor affecting theaccuracy of the measurement especially at high temperature. Although Ar was inadequate forthis purpose on account of its large disturbing effects on the oscillation, in He atmosphere these effectswere remarkably small. Therefore, the use of He was considered to be preferable.
(3) From a series of experimental analysis, it was confirmed that under the suitable experimentalcondition it was possible to measure the viscosity of liquid metals and alloys at high temperature with sufficient accuracy using the apparatus presented in this paper.